Iran today rejected any modification of its nuclear deal with world powers after US President Donald Trump demanded tough new measures to keep the agreement alive.

Iran "will not accept any amendments in this agreement, be it now or in the future, and it will not allow any other issues to be linked to the JCPOA", the foreign ministry said in a statement, using the 2015 deal's technical name.

It has the backing of all the partners to the agreement apart from the United States, with Russia warning Washington that withdrawing would be "a big miscalculation".

"This could be one of Washington's big foreign policy mistakes," he added.

Trump again waived nuclear-related sanctions yesterday - as required every few months to stay in the agreement - but demanded that European partners work with Washington to "fix the deal's disastrous flaws, or the United States will withdraw".

He said the new deal should curb Iran's missile programme and include permanent restrictions on Iran's nuclear plants, removing expiration dates due to kick in after a decade.

The other parties to the agreement - Britain, China, France, Germany, Russia and the European Union - have all said the deal is working and that Iran is complying fully with its commitments.

Britain and Germany said yesterday they had taken note of Trump's latest decision and would confer with France before responding.

On the streets of Tehran, many have grown cynical and exasperated by the endless pressure from the United States.

"It doesn't make any difference. We have been under US sanctions for the last 40 years," said Farshad Alyan, a 26- year-old law student.

"Two years ago when the JCPOA was signed we were so hopeful. We don't have that hope any more."

Iran argues that continued US sanctions on non-nuclear areas such as human rights and missile testing have effectively barred it from gaining many of the financial benefits expected from the deal.

Foreign Minister Mohammad Javad Zarif has said Trump's aggressive stance on the deal and Iran generally have also violated the commitment to "refrain from any policy specifically intended to directly and adversely affect the normalisation of trade and economic relations with Iran" in the accord.

"Trump has once again avoided the nuclear option on the nuclear deal. But the clear reluctance with which he has issued the sanctions waivers will continue to weigh on the business community," said Esfandyar Batmanghelidj, founder of the Europe-Iran Forum, a business network.

"However, if the 'adults in the room' prevailed this time and kept Trump from exiting the deal, there remains hope they will prevail in the end," he added.

Responding to Trump's speech late yesterday, Zarif tweeted: "Rather than repeating tired rhetoric, US must bring itself into full compliance - just like Iran."

Today's statement from Iran's foreign ministry further criticised new sanctions on 14 individuals announced by the US Treasury yesterday over human rights issues and Iran's missile programme.

In particular, placing judiciary chief Ayatollah Sadegh Larijani on the sanctions list "crossed all red lines of conduct in the international community... and the government of the United States will bear responsibility for all the consequences of this hostile move".

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)